1. Field of the Invention
This invention relates to intravascular devices for implantation within a vessel of the body, and more particularly to a stent device which may be used in the treatment of blood vessel disorders. More specifically, the intravascular device may take the form of an aneurysm cover to be used in the treatment of aneurysms which occur in the brain.
2. Description of the Prior Art
On a worldwide basis, nearly one million balloon angioplasties were performed in 1997 to treat vascular disease, including blood vessels clogged or narrowed by a lesion or stenosis. The objective of this procedure is to increase the inner diameter or cross-sectional area of the vessel passage, or lumen, through which blood flows.
Another serious vascular defect is an area of weakened vessel wall that causes a bulge, or bubble, to protrude out in a radial direction from the vessel. This type of defect is called an aneurysm. If untreated, the aneurysm may continue expanding until it bursts thereby causing hemorrhaging from the vessel.
In an effort to prevent restenosis or treat an aneurysm without requiring surgery, short flexible cylinders or scaffolds, made of metal or polymers, are often placed into a vessel to maintain or improve blood flow. Referred to as stents, various types of these devices are widely used for reinforcing diseased blood vessels, for opening occluded blood vessels, and for defining an internal lumen to relieve pressure in an aneurysm. The stents allow blood to flow through the vessels at an improved rate while providing the desired lumen opening or structural integrity lost by the damaged vessels. Some stents are expanded to the proper size by inflating a balloon catheter, referred to as xe2x80x9cballoon expandablexe2x80x9d stents, while others are designed to elastically resist compression in a xe2x80x9cself-expandingxe2x80x9d manner.
Balloon expandable stents and self-expanding stents are generally delivered in a cylindrical form, crimped to a smaller diameter and are placed within a vessel using a catheter-based delivery system. When positioned at a desired site within a vessel, these devices are expanded by a balloon, or allowed to xe2x80x9cself-expand,xe2x80x9d to the desired diameter.
One such stent for treatment of abdominal aortic aneurysms is disclosed in U.S. Pat. No. 6,267,783 to Robert P. Letendre, et al. This patent discloses a self-expanding stent which may be used in the treatment of aortic aneurysms. This device may be easily recaptured after placement and repositioned to a new position within the vessel. This patent, assigned to a related company, is subsequently referred to and the disclosure therein is incorporated and made a part of the subject patent application.
Another stent aneurysm treatment device is disclosed in U.S. Pat. No. 6,361,558, assigned to the same assignee as the present application. This patent discloses vasculature stents of various configurations which may be used as aneurysm covers for occluding, or partially occluding, aneurysms located at various positions along the blood vessels.
There is a need for an improved stent which may be easily delivered to a vasculature site through a very small catheter, is capable of being repositioned and which exhibits sufficient structural integrity and resilience under radial compressive forces. More particularly, there is a need for such a stent that, in its compressed state prior to delivery of the stent, has a diameter which is extremely small. Such a stent could be placed in a very small microcatheter for subsequent positioning within a vessel of the human brain. Obviously, such vessels are extremely small and very tortuous throughout their length.
In accordance with one aspect of the present invention, there is provided a self-expanding stent which includes a small diameter skeletal tubular member. The skeletal tubular member is comprised of a plurality of cells which are formed by a plurality of interconnected, non-inverted horizontal and inverted horizontal S-shaped members. The S-shaped members are generally parallel to the longitudinal axis of the tubular member and are interconnected in a repeating pattern. Each of the S-shaped members has a proximal end, a distal end, a proximal intermediate section and a distal intermediate section. The proximal end of each non-inverted horizontal S-shaped member is attached to the distal intermediate section of an adjacent inverted horizontal S-shaped member, the distal end of each non-inverted horizontal S-shaped member is attached to the proximal intermediate section of another adjacent inverted horizontal S-shaped member, the proximal end of each inverted horizontal S-shaped member is attached to the distal intermediate section of an adjacent non-inverted horizontal S-shaped member, and the distal end of each inverted horizontal S-shaped member is attached to said proximal intermediate section of another adjacent non-inverted horizontal S-shaped member. With this configuration, the skeletal tubular member may be compressed to a very small diameter because of xe2x80x9cnestingxe2x80x9d of adjacent S-shaped members.
In accordance with another aspect of the present invention, as the skeletal tubular member is compressed into a small diameter, each proximal intermediate section of each non-inverted horizontal S-shaped member pulls on a distal end of an adjacent inverted horizontal S-shaped member, each distal intermediate section of each non-inverted horizontal S-shaped member pulls on a proximal end of another adjacent inverted horizontal S-shaped member, each proximal intermediate section of each inverted horizontal S-shaped member pulls on the distal end of an adjacent non-inverted horizontal S-shaped member, and each distal intermediate section of each inverted S-shaped member pulls on the proximal end of an adjacent non-inverted horizontal S-shaped member thereby causing the xe2x80x9ccellsxe2x80x9d of the S-shaped member, xe2x80x9cnestxe2x80x9d and cause the tubular member to attain the small diameter.
In accordance with another aspect of the present invention, the skeletal tubular member includes at least two proximal legs which are attached to the skeletal tubular member and which extend generally parallel to the longitudinal axis of the tubular member. At least one of the proximal legs includes a T-shaped flange adjacent to the end of the proximal leg for attachment to a stent release mechanism.
In accordance with another aspect of the present invention, the legs are biased outwardly away from the longitudinal axis of the skeletal tubular member. The legs may also include radiopaque markers for providing an indication of the location of the stent device as the device is positioned within a vessel.
In accordance with still another aspect of the present invention, the skeletal tubular member may include distal legs which are attached to and extend generally parallel to the longitudinal axis of the skeletal tubular member. These legs may also include radiopaque markers for providing positioning information.
In accordance with still another aspect of the present invention there is provided a self-expanding stent device which includes a small diameter skeletal tubular member. The wall of the skeletal tubular member is comprised of a plurality of cells which are formed by interconnected sinusoidal members. The sinusoidal members are generally parallel to the longitudinal axis of the tubular member. Each sinusoidal member extends for one and a half sinusoidal periods, or about 540 degrees. Each sinusoidal member has a proximal end, a distal end, a proximal peak and a distal peak. The sinusoidal members have a repeating pattern in which the proximal end of each sinusoidal member is attached to the distal peak of an adjacent sinusoidal member. Also, the distal end of each sinusoidal member is attached to the proximal peak of another adjacent sinusoidal member.
In accordance with another aspect of the present invention, in its compressed state, the proximal peak of each sinusoidal member pulls the distal end of an adjacent sinusoidal member and the distal peak of each sinusoidal member pulls the proximal end of an adjacent sinusoidal member causing the cells of the wall to collapse, or xe2x80x9cnest,xe2x80x9d thereby allowing the skeletal tubular member to attain a small compressed diameter.
In accordance with still another aspect of the present invention, a self-expanding aneurysm cover is provided which when placed across an aneurysm of a blood vessel reduces, or obstructs, the flow of blood between the aneurysm and its related blood vessel. The aneurysm cover includes a small diameter skeletal tubular member which is comprised of a plurality of cells which are formed by a plurality of interconnected, non-inverted horizontal and inverted horizontal S-shaped members. The S-shaped members are generally parallel to the longitudinal axis of the tubular member and are interconnected in a repeating pattern. Each of the S-shaped members has a proximal end, a distal end, a proximal intermediate section and a distal intermediate section. The proximal end of each non-inverted horizontal S-shaped member is attached to the distal intermediate section of an adjacent inverted horizontal S-shaped member, the distal end of each non-inverted horizontal S-shaped member is attached to the proximal intermediate section of another adjacent inverted horizontal S-shaped member, the proximal end of each inverted horizontal S-shaped member is attached to the distal intermediate section of an adjacent non-inverted horizontal S-shaped member, and the distal end of each inverted horizontal S-shaped member is attached to said proximal intermediate section of another adjacent non-inverted horizontal S-shaped member. With this configuration, the skeletal tubular member may be compressed to a very small diameter because of xe2x80x9cnestingxe2x80x9d of adjacent S-shaped members.
These and other aspects of the invention and the advantages thereof will be clearly understood from the following description and drawings of a preferred embodiment of the present invention.